Strain-Based Design Model for FRP-Confined Concrete Columns


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Title: Strain-Based Design Model for FRP-Confined Concrete Columns

Author(s): N. Saenz and C.P. Pantelides

Publication: Special Publication

Volume: 230


Appears on pages(s): 1011-1028

Keywords: confinement; constitutive model; stress-strain relationships

Date: 10/1/2005

A constitutive strain-based confinement model is developed herein forcircular concrete columns confined with fiber reinforced polymer (FRP) composites. Aseries of relationships were developed from experimental data, which facilitated theestablishment of the strain-based model. The FRP-confined concrete constitutivemodel calculates the internal damage of the column by using the radial strain. Theradial and axial strains at zero volumetric strain were used to mark the beginning ofeffective dilation response of the FRP composite jacket. The secant concrete moduluswas used in the model and expressed as a function of the secant modulus softeningrate, which depends on the ultimate radial to axial strain ratio. The experimentalrelationship for the ultimate radial to axial strain ratio is a function of the normalizedeffective confining stiffness. The secant modulus softening rate is constant throughoutthe plastic stress-strain response until failure. The FRP-confined concrete constitutivemodel evaluates the ultimate radial strain, which was related to the FRP compositeeffectiveness. The FRP-confined concrete model predicts the stress-strain responseaccurately for any normalized effective confinement stiffness.